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From: feg@moss.ATT.COM (Forrest Gehrke,2C-119,7239,ATTBL)
Newsgroups: comp.sys.ibm.pc
Subject: Re: GAS PLASMA SCREENS!!
Message-ID: <5095@cbnewsl.ATT.COM>
Date: 12 Apr 90 15:01:21 GMT
References: <26226d66.1467@petunia.CalPoly.EDU> <140@demott.COM>
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Organization: AT&T Bell Laboratories
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In article <140@demott.COM>, kdq@demott.COM (Kevin D. Quitt) writes:
> In article <26226d66.1467@petunia.CalPoly.EDU> jdudeck@polyslo.CalPoly.EDU (John R. Dudeck) writes:
> >
> >CRT's DO NOT emit any radiation other than visible light!
> 
>     You're making a joke, right? Besides the RF they produce at both
> horizontal and vertical scanning frequencies (plus harmonics, plus
> hetrodynes), and besides the electrons that get through the phosphor,
> color CRTs give off xrays, mostly in the direction of the user. 
> 
Before spouting off for the whole world, please determine some facts.
If you pasted a piece of X-ray photographic film on the face of a
color crt for a month, you MIGHT, just might, find a faint amount
of evidence of X-ray emission.  Faces of crt are fairly thick and
are made of lead glass.  Any x-ray emission through lead glass had
better be damned energetic.  X-ray emission from the much higher
voltage TV color CRT's is still soft x-rays and is mostly emitted
from the edges of the CRT where the glass envelope is much thinner.
All manufacturers are aware of this and are required to provide
shielding in the outer edge areas.  Still, this is soft xrays and
you would have to have your face up against the glass for hours
to get any amount of penetration from this radiation.

If you can find any electrons penetrating the glass face you are
a better magician than Houdini ever was.

As to RF at the low frequencies involved (just above the audible
range--15khz for most, up to 35 khz for some of the VGA's) and
the low power, if you can find time to worry about that, you
should definitely avoid driving past standard broadcast
antenna farms.  The main concern with PC's is the RFI they
produce for desired radio reception, not the other way 
around.  This is why the FCC requires certification from
PC manufacturers.

Forrest Gehrke feg@dodger.ATT.COM